Question

cos(7pi/8)

Answer 1

Ah. Looks like (7pi/8) is in radians. To use cos and to make your life easier, convert 7pi/8 into degrees.

The conversion for radians into degrees is: 180/pi radians.

Basically, convert 7pi/8 into degrees, then find the cos of the converted amount.

Hopefully that helps. Feel free to ask any more questions if you need help or clarification! :D

Answer 2

Oops. Forgot to add that to convert radians into degrees, multiply 7pi/8 by 180/pi. :)